Variable Interest Entities - Consolidated VIEs (Details) - USD ($) $ in Millions	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Carrying amounts of consolidated VIE assets and liabilities
Total assets	$ 271,309.4		$ 276,087.8
Total liabilities	255,725.7		261,137.1
Redeemable noncontrolling interest	272.7	$ 239.7	264.9	$ 304.5	$ 537.7	$ 391.2
Aggregate consolidated variable interest entities
Carrying amounts of consolidated VIE assets and liabilities
Total assets	37,665.2		40,802.1
Total liabilities	36,492.7		39,713.7
Redeemable noncontrolling interest	197.5		215.4
Grantor trust
Carrying amounts of consolidated VIE assets and liabilities
Total assets			99.9
Total liabilities			98.6
Mandatory retirement savings funds
Carrying amounts of consolidated VIE assets and liabilities
Total assets	36,849.1		39,891.1
Total liabilities	36,454.6		39,524.9
Real estate VIE
Carrying amounts of consolidated VIE assets and liabilities
Total assets	452.8		479.7
Total liabilities	29.8		88.0
Sponsored investment funds
Carrying amounts of consolidated VIE assets and liabilities
Total assets	363.3		331.4
Total liabilities	8.3		2.2
Redeemable noncontrolling interest	$ 197.5		$ 215.4